1. Field of Invention
The present invention relates to a semiconductor memory device and an operating method thereof.
2. Description of Related Art
A semiconductor memory device performs a program verifying method of verifying whether or not a program operation is being normally performed.
The semiconductor memory device verifies through the program verifying method only on whether or not the program of every memory cell coupled to selected page is finished in the initial stages. However, a program verifying method, of counting the number of memory cells of which the program is not finished of every memory cell coupled to the selected page, has been developed.
A current sensing method, which is one of the various program verifying methods, may sense the number of failed memory cells in a comparatively rapid time of period, and thus it has been widely used. However, a problem exists in that accuracy of the current sensing method starts to deteriorate in proportion to a rapid velocity because the current sensing method receives a united program verifying result of every memory cell coupled to the selected pages.
Specially, a method of counting more accurately the number of failed memory cells with performing a program verifying operation in a rapid time of period has been required as the capacity of the semiconductor memory device increases and fine processes are performed.